Axionic Strings, Domain Walls and Baryons

When axionic strings carry a global charge, domain walls bounded by such strings may not be allowed to decay completely. This happens in particular in some models where a composite axion-like particle is the pseudo-Nambu-Goldstone boson of chiral symmetry breaking of an extra quark flavor. In this case the global symmetry is the extra flavor baryonic symmetry. The corresponding axionic domain walls can carry a baryonic charge: they represent the low energy description of the baryons made by the extra quark flavor. Basic properties of these particles, such as spin, mass scale, size are discussed. The corresponding charged axionic strings are explicitly constructed and studied in a specific calculable model.